From Ice to Glass: Historical Cryobiological Events that Transformed the Application of Assisted Reproductive Technologies

In the late 1700s while conducting insemination experiments with dogs, frogs, and fish, an Italian priest, Lazzaro Spallanzani, made the seminal observation that fish sperm could be reduced to a state of complete inactivation during cooling and then revived when warmed [1]. A decade later, Montegazza was the first to conceive the idea of frozen human sperm banks, suggesting that a dying soldier might beget his semen frozen and stored at home to a legal heir [2, 3]. Fifty years later, a century of cryobiological discovery and the continual process of rediscovery through experimentation led to the breakthrough knowledge facilitating the highly efficient cryopreservation and global use of reproductive cells and tissues. Today, we stand on the shoulders of giants who sought to question the principles of ice growth in solutions and inside cells, and how vitreous glass phases can occur and be maintained. They learned that permeating (e.g., glycerol, DMSO, and glycols) and non-permeating (e.g., sugars) solutes could be used as cryoprotective agents for mitigating the cellular injury of solution effects or physically damaging ice formation events during cooling and rewarming. Tens of thousands of historical publications could be cited, but the best this chapter can do is highlight the seminal achievements of pioneers who dared to question and those that transformed theory into biological applications which regenerated life. Each of them was inspired by the scientific progress and theories of others, which have been referenced in their papers.